From mboxrd@z Thu Jan 1 00:00:00 1970 From: stanimir.varbanov@linaro.org (Stanimir Varbanov) Date: Tue, 8 Dec 2015 11:01:04 +0200 Subject: [PATCH v4 1/5] PCI: designware: add memory barrier after enabling region In-Reply-To: <1449149725-27607-2-git-send-email-stanimir.varbanov@linaro.org> References: <1449149725-27607-1-git-send-email-stanimir.varbanov@linaro.org> <1449149725-27607-2-git-send-email-stanimir.varbanov@linaro.org> Message-ID: <56669C50.9060700@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 12/03/2015 03:35 PM, Stanimir Varbanov wrote: > Add 'write memory' barrier after enable region in PCIE_ATU_CR2 > register. The barrier is needed to ensure that the region enable > request has been reached it's destination at time when we > read/write to PCI configuration space. > > Without this barrier PCI device enumeration during kernel boot > is not reliable, and reading configuration space for particular > PCI device on the bus returns zero aka no device. Anand, Jingoo, what is your opinion? > > Signed-off-by: Stanimir Varbanov > --- > drivers/pci/host/pcie-designware.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/pci/host/pcie-designware.c b/drivers/pci/host/pcie-designware.c > index 02a7452bdf23..ed4dc2e2553b 100644 > --- a/drivers/pci/host/pcie-designware.c > +++ b/drivers/pci/host/pcie-designware.c > @@ -164,6 +164,11 @@ static void dw_pcie_prog_outbound_atu(struct pcie_port *pp, int index, > dw_pcie_writel_rc(pp, upper_32_bits(pci_addr), PCIE_ATU_UPPER_TARGET); > dw_pcie_writel_rc(pp, type, PCIE_ATU_CR1); > dw_pcie_writel_rc(pp, PCIE_ATU_ENABLE, PCIE_ATU_CR2); > + /* > + * ensure that the ATU enable has been happaned before accessing > + * pci configuration/io spaces through dw_pcie_cfg_[read|write]. > + */ > + wmb(); > } > > static struct irq_chip dw_msi_irq_chip = { > -- regards, Stan